FAST MODE DECISION ALGORITHM FOR INTRA PREDICTION IN HEVC

INTERIM REPORT

Lanka Naga Venkata Sai Surya Teja

Student ID 1000916473

Mail ID nvssurya.lanka@mavs.uta.edu

Date 04/24/2014

UNDER THE GUIDANCE OF

Dr. K. R. Rao

PROPOSAL

• To improve the coding efficiency of intra frame coding, up to 34 intra prediction modes are defined in High Efficiency Video Coding (HEVC) [1]

• The best mode among these pre-defined intra prediction modes is selected by rate-distortion optimization (RDO) for each block

• This project proposes a new method to reduce the candidates in RDO process, as it will be time-consuming if all directions are tested in the RDO process when compared with the default method of intra prediction in HM 13.0.

• Also analysis of PSNR, BD- PSNR, BD- Bitrate can be done by comparing with the default encoding scheme in HM 13.0 [5].

INTRODUCTION

• HEVC standard [2] provides a highly flexible hierarchy of unit representation which consists of three block concepts: coding unit (CU), prediction unit (PU), and transform unit (TU).

• This separation of the block structure is helpful for each unit of optimization.

• CU is a macroblock-like unit of region splitting which is always square and its size can be from 8x8 luma samples up to the largest coding units (LCUs).

• The PU is used only for the CU which is the leaf node in the Quadtree structure and the size of two PUs are 2Nx2N and NxN.

• The third block concept transform unit size cannot exceed that of the CU.

BLOCK DIAGRAM OF HEVC ENCODER[15]

BLOCK DIAGRAM OF H.264 ENCODER[20]

BLOCK DIAGRAM OF HEVC DECODER[15]

• Since encoder needs to exhaust all the combinations of CU, PU and TU to find the optimal solutions, it is very time-consuming

• The encoder will not tolerate it if all the directions are employed in the rate-distortion optimization process

• To reduce the computational complexity of the encoder, a fast intra mode decision [4] was adopted in HM13.0 [5]

CODING TREE ALGORITHM

OVERVIEW OF INTRA PREDICTION

• In H.264, intra prediction [6][7][8][9] is based on spatial extrapolation of samples from previously decoded image blocks, followed by integer discrete cosine transform (DCT) [10] based coding

• HEVC utilizes the same principle, but further extends it to efficiently represent wider range of textural and structural information in images

• HEVC contains several elements improving the efficiency of intra prediction over earlier solutions

HEVC INTRA PREDICTION MODES [7]

H.264 INTRA PREDICTION MODES[21]

METHOD PROPOSED FOR FAST MODE DECISON ALGORITHM FOR INTRA

PREDICTION• The fast intra prediction consists of three steps:

1. Hadamard Transformed Coefficients Of Residual Signal[13]

2. Progressive Mode Search[13]

3. Early RDOQ Termination[13]

TEST SEQUENCES

• [1] BQSquare_416x240_60

• [2] BQMall_ 832x480_60

• [3] KristenAndSara_1280x720_60

EXPERIMENTAL RESULTS of BQMall_832x480_60

Analysis of results for unmodified method with number of frames 10

QP BITRATE(kbps)

PSNR(avg)db

ENCODING TIME(sec)

24 23754.8160

41.137 176.624

28 16010.5920

38.6744 161.116

32 10612.8000

36.2830 151.866

34 8447.7600

34.9856 134.619

Analysis of results for modified method with number of frames 10QP BITRATE

(kbps)PSNR(avg)db

ENCODING TIME(sec)

24 24046.1849

40.9975 134.234

28 16227.4525

38.5344 120.837

32 10718.928

36.1320 112.380

34 8532.2376

34.8473 98.271

EXPERIMENTAL RESULTS of BQMall_832x480_60

Analysis of results for unmodified method with number of frames 30

QP BITRATE(kbps)

PSNR(avg)db

ENCODING TIME(sec)

24 23836.5280

41.1352 519.561

28 16075.4080

38.6716 515.1675

32 10704.5280

36.2715 426.831

34 8506.4960

34.9803 407.187

Analysis of results for modified method with number of frames 30QP BITRATE

(kbps)PSNR(avg)db

ENCODING TIME(sec)

24 24074.8932

40.9944 396.944

28 16236.1620

38.5300 383.799

32 10811.5732

36.1225 312.44

34 8591.5609

34.8425 297.246

Encoding Time Vs QP

For number of frames 10 For number of frames 30

24 28 32 340.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

180.00

200.00

Encoding Tme(sec) for unmodifed methodEncoding Time (sec) for modified method

QP

Encoding Ti

me(sec)

24 28 32 340

100

200

300

400

500

600

Encoding Tme(sec) for unmodifed methodEncoding Time (sec) for modified method

QP

Encoding ti

me(sec)

PSNR (avg) vs Bitrate

For number of frames 10 For number of frames 30

5000 10000 15000 20000 2500030

32

34

36

38

40

42

Chart Title

For unmodified methodFor modified method

Bitrate(kbps)

PSNR(avg)dB

5000 10000 15000 20000 25000 3000030

32

34

36

38

40

42

Chart Title

For unmodified methodFor modified method

Bitrate (kbps)

PSNR (avg)

CONCLUSION

For the HM13.0 with fast mode decision algorithm method compared to unmodified HM13.0,• 0.1-0.5 dB loss in the PSNR• 11-15 kbps increase in the bitrate• 20-28 % reduction in encoding time

WQVGA – SD sequences of 10 frames and 30 frames each were tested from QPs 24, 28,32,34. Visual quality was maintained.

Future Work

• BD-PSNR and BD-bitrate can be compared for default method and proposed method

• Also proposes a new method to reduce the candidates in RDO process, as it will be time-consuming if all directions are tested in the RDO process.

ACRONYMS• BD- Bitrate - Bjøntegaard Delta Bitrate• BD- PSNR - Bjøntegaard Delta Peak Signal-to-Noise Ratio• CU - Coding Unit• DCT - Discrete Cosine Transform• DST - Discrete Sine Transform• HEVC - High Efficiency Video Coding• JCT- VC- Joint Collaborative Team on Video Coding• LCU - Largest Coding Unit• MPM - Most Probable Mode• PSNR - Peak Signal-to-Noise Ratio• PU - Prediction Unit• QP - Quantization Parameter• RDOQ - Rate Distortion Optimization Quantization• RDO - Rate- Distortion Optimization• RMD - Rough Mode Decision• SSIM - Structural Similarity Index• TU - Transform Unit

REFERENCES

[1] G.J. Sullivan et al, Overview of the high efficiency video coding (HEVC) standard‖, IEEE Trans. circuits and systems for video technology, vol. 22, no.12, pp. 1649 – 1668, Dec 2012.

[2] JCT-VC, “WD1: Working Draft 1 of High-Efficiency Video Coding”, JCTVC-C403, JCT-VC Meeting, Guangzhou, October 2010.

[3] Coding tree structure - https://www.google.com/search?q=coding+tree+structure+in+hevc

[4] Y. Piao et al, “Encoder improvement of unified intra prediction,” JCTVC-C207, Guangzhou, October 2010.

[5] Software for HEVC - https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware

[6] T.L. Silva et al, ”HEVC intra coding acceleration based on tree inter-level mode correlation”, SPA 2013 Sep.2013, Poznan, Poland

[7] H. Zhang and Z. Ma, ”Fast intra prediction for high efficiency video coding ”, Pacific Rim Conf. on Multimedia, PCM2012, Singapore, Dec. 2012.

[8] M. Zhang et al, ”An adaptive fast intra mode decision in HEVC ”, IEEE ICIP 2012, pp.221-224, Orlando, FL, Sept.- Oct. 2012.

[9] Y. Kim et al, “A fast intra-prediction method in HEVC using rate-distortion estimation based on Hadamard transform”, ETRI Journal, vol.35, #2, pp.270-280, Apr. 2013.

[10 ]A. Saxena and F. Fernanades, “Mode dependent DCT/DST for intra prediction in block based image/video coding”, IEEE ICIP, pp. 1685-1688, Sept. 2011.

[11] M. Khan et al, “An adaptive complexity reduction scheme with fast prediction unit decision for HEVC Intra encoding”, IEEE ICIP, pp. 1578-1582, Sept. 2013.

[12] P. Mehta, “Complexity reduction for intra mode selection in HEVC using OpenMP”, course website: http://www-ee.uta.edu/Dip/Courses/EE5359/ Section: previous projects, Sub section: Projects (Spring 2014).

[13] S. Vasudevan, “Fast intra prediction and fast residual quadtree encoding implementation in HEVC”, course website: http://www-ee.uta.edu/Dip/Courses/EE5359/ Section: previous projects, Sub section: Projects (Spring 2014).

[14] K.R.Rao , D. N. Kim and J.J. Hwang ,” Video coding standards: AVS China, H.264/MPEG-4 Part10, HEVC, VP6, DIRAC and VC-1"´, Springer, 2014.

[15] G.Sullivan et al, “Standard Extensions of the High Efficiency Video Coding (HEVC) Standard” Journal of Special Topics in Signal Processing, vol.7, No. 6, pp. 1001-1016, Dec 2013.

[16] Test Sequences: ftp://ftp.kw.bbc.co.uk/hevc/hm-11.0-anchors/testsequences/

[17] F. Bossen et al, "HM Software Manual", JCT-VC of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, AHG chairs, January 2014

[18] B. Bross et al, “High Efficiency Video Coding (HEVC) Text Specification Draft 10”, Document JCTVC- L1003, ITU-T/ISO/IEC Joint Collaborative Team on Video Coding (JCT-VC), Mar. 2013 available on http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=7243

[19] JVT Draft ITU-T recommendation and final draft international standard of joint video specification (ITU-T Rec. H.264-ISO/IEC 14496-10 AVC), March 2003, JVT-G050 available on http://ip.hhi.de/imagecom_G1/assets/pdfs/JVT-G050.pdf

• [22] Special issue on emerging research and standards in next generation video coding, IEEE Transactions on Circuits and Systems for Video Technology (CSVT), vol.22, pp. 1646-1909, Dec. 2012.

• [23] Special issue on emerging research and standards in next generation video coding, IEEE Transactions on Circuits and Systems for Video Technology (CSVT), vol.23, pp. 2009-2142, Dec. 2013.

• [24] IEEE Journal of Selected Topics in Signal Processing, Vol. 7, pp. 931 -1151, Dec. 2013.